MeVisLab is available for Windows, Linux, and macOS. You can download it from the official webpage (you don't need a license for running these networks). Each network is identified by the file extension .mlab. You can open the network from MeVisLab by clicking on File->Open and select the .mlab file you want to open. For each network, there is an accompanying document that gives a general overview of the functionality of the network. For some networks, example data is also provided.
If you have any questions regarding a specific MeVisLab network, please contact the corresponding ESR.